In many fields of workpiece processing, use is made of tools and materials, which comprise abrasive particles which are to be set in contact with workpieces to be processed. These tools and materials can be commonly designated “abrasive products”. The processing may be polishing, grinding, cutting or other mechanical work. In these products, the abrasive particles, which are of sufficient hardness, are fixed to a support, which can take a variety of shapes.
One example of aforementioned tools is a grinding wheel. Grinding wheels are conventionally made of natural or synthetic abrasive particles fixed together in a matrix by means of binder. In manufacturing of a grinding wheel, the components (abrasive particles, binder) are mixed together and molded under pressure to achieve the desired shape and compact structure. After the molding, the binder is allowed to cure, or the grinding wheel is fired if the binder is ceramic.
Cutting wheel is another example of a tool which contains abrasive particles and which can be used for workpiece processing by cutting through material. The manufacture of a cutting wheel comprises similar steps as mentioned above. Some tools can be used both as grinding wheels and cutting wheels.
The abrasive materials also include various abrasive cloths, abrasive nets, abrasive 3-dimensional fiber materials, abrasive papers, abrasive filaments etc., where the support is in form of a textile or paper structure or film. These materials are flexible and can be used especially in polishing and surface finishing. In manufacturing these materials, abrasive particles are usually fixed on the supporting material with the help of a resin binder. Also metals and melted non organic materials such as glass can be used as binders.
Various organic binders, like phenolic resins, are commonly used to connect and stabilize abrasive grains in various grinding products, like in cutting wheels, grinding wheels etc. The resin has, however, a tendency to fill also the pores between the grains, decreasing the number of available edges of the abrasive grains for working the material. This will result in insufficient efficiency, and the surface containing the abrasive particles must be pressed harder against the workpiece to achieve the same result, which will cause excess heat from friction. Temperature stability of the resin phase is often relatively low and the product may break or degrade due to this excess heat arising from the friction. Different type of low density fillers, such as hollow spheres, are used to decrease the density in the product. The tendency is, however, that low density fillers have a negative influence on the strength of the end product.
Another problem in the manufacturing of abrasive products is heterogeneous distribution of the abrasive grains in the continuous matrix. This problem can be avoided by increasing viscosity of the unhardened composition, which may lead to problems in the deposition of the mixture eg. in spray coating of abrasive non wovens and cloths. Thus, there is a need for additive that can stabilize heavy grains and simultaneously allow easy spraying or coating of the formulation.
Porosity also allows room for small chips of metal, known as swarf, and abrasive generated during the grinding process. Porosity also provides pathways that carry fluids used to control heat and improve the cutting characteristics of the abrasive grains. Without adequate porosity and spacing between abrasive grains, the wheel can become loaded with swarf and cease to cut properly.
Thus, the problems associated with materials and tools where resin binders, such as commonly used phenolic resins are used for fixing the abrasive particles, is that the binder tends to fill the pores between the abrasive particles, which lowers the number of active grinding edges. If sufficient porosity can be created for example due to the structure of the support, the problem of even distribution of the particles, their fixation to the support, and the permanence of the fixation still remains.